/Engine/Source/Editor/SequencerCore/Public/MVVM/Extensions/ISortableExtension.h
Compare custom orders (if both set), priorities, and identifiers
static bool CompareCustomOrderFirst ( const [FSortingKey](API\Editor\SequencerCore\MVVM\Extensions\FSortingKey) & A, const [FSortingKey](API\Editor\SequencerCore\MVVM\Extensions\FSortingKey) & B )